Railways – Car-carried propulsion system – Electric
Reexamination Certificate
2000-03-09
2001-09-11
Pape, Joseph D. (Department: 3612)
Railways
Car-carried propulsion system
Electric
C104S292000, C104S294000, C104S282000, C310S012060, C310S013000, C318S135000
Reexamination Certificate
active
06286434
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a propulsion system for a magnetically levitated vehicle.
BACKGROUND INFORMATION
A propulsion system for a magnetically levitated vehicle is described in, for example, from “Magnetbahn TRANSRAPID—Die neue Dimension des Reisens” (TRANSRAPID magnetic railway, the new dimension in travel) Hestra Verlag Darmstadt, 1989, ISBN
3-7771-0208-3
, pages
76-79
. The propulsion system of a magnetically levitated vehicle fulfills three functions, namely suspension, guidance and driving of the magnetically levitated vehicle on a guideway without contact. The propulsion system for it includes a suspension system, a guidance system and a drive system. The conventional guidance system includes a guidance magnet arrangement with the guidance magnets being arranged laterally so that the magnetic flux runs perpendicular to the longitudinal direction of the lateral guide rails in the vehicle, thereby ensuring lateral guidance of the magnetically levitated vehicle. Pairs of suspension magnets mounted in the lower area of the suspension frame of the magnetically levitated vehicle assume the suspension function. The required induction also provides the energization for the drive, so that the suspension system and the drive system are formed by one and the same magnet arrangement and the functions are mutually interdependent. Core assemblies are provided in the guideway for these suspension and drive magnet arrangements. The core assembly provided for the suspension and drive magnets contains a current-carrying traveling-field winding and forms the stator of a linear synchronous long-stator drive.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,605,100 describes a propulsion system for a magnetically levitated vehicle, where the drive magnets mounted in the vehicle together with current conductors provided in the guideway form a d.c. drive system. The drive magnets are arranged in such a way that they generate a horizontal magnetic field which passes through the guideway stator holding the electric conductors. The guideway is therefore subdivided into a plurality of small sections, each being supplied with a direct current that can be switched on and off, so that only the electric conductors in the vicinity of the two magnet poles of a drive magnet surrounding the stator are electrically conducting. With this conventional propulsion system, each section of the stator must be smaller than the width of the drive magnet, because otherwise the current is displaced by the drive magnet and flows in areas of the stator where it cannot contribute toward the development of thrust. This yields the necessity of using a plurality of high-speed electronic switches, leading to high investment and maintenance costs.
A linear d.c. drive system described in Philips techn. Rev. 40, 1982, No. 11/12, pp. 329-337, has a drive magnet on opposite sides of a linear stator provided with a coil winding, with its magnetic axis in each case running horizontally, so that one pole of the drive magnet faces the stator and the other pole of the drive magnet faces away from the stator. Therefore, only a portion of the magnetic field generated by the drive magnet contributes toward the creation of linear thrust. Furthermore, additional iron cores must also be arranged on the outsides of the guideway to prevent portions of the magnetic field generated by the drive magnets and facing away from the stator from flowing over the stator in reverse, thus having a negative effect on thrust.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a propulsion system for a magnetically levitated vehicle that reduces the technical complexity particularly of the equipment required for a great length on the guideway, including in particular guideway, stator and feeder cable.
According to the present invention, this object is achieved by providing a propulsion system having a drive system which includes a drive magnet arrangement mounted in the vehicle, a linear d.c. motor being formed with a stator provided with a winding and extending in the longitudinal direction of the guideway. Drive magnets are arranged with their magnetic axes that connect the two magnet poles running across the longitudinal direction of the guideway so that the magnet poles arranged in succession in the longitudinal direction have the same polarity, and the magnet poles belonging to a drive magnet are each arranged on one side of the stator so they are facing the stator.
The magnets in the vehicle required for driving are thus arranged so that they do not induce any alternating fields in the guideway. In other words, the magnetic flux induced in the guideway has the same direction over the entire length of the vehicle, and there is no change of polarity as the magnetically levitated vehicle passes by.
Since the magnet poles of each drive magnet are arranged on one side of the stator and are facing it, the largest possible portion of the magnetic field running outside the drive magnet is injected into the stator and is thus effective in generating thrust.
Since the drive magnets in the stator do not induce any alternating fields in passing by, the stator can be made of solid ferromagnetic steel. This reduces the cost of manufacturing the stator, because no core assemblies or screw connections are required.
Direct currents are supplied for operating the linear d.c. motor, so this also eliminates the power inverters and transformers in the substations and the respective switchgear. In addition, the reactive power demand approaches zero. Furthermore, a very simple control is possible, because it is not necessary to determine and process the frequency and phase. This greatly simplifies the data transfer between the vehicle and the substation required for the operation of the magnetically levitated vehicle. Since no alternating fields are induced, there is also no hysteresis loss.
The drive magnets may be arranged vertically with their magnetic axes running between the two magnet poles.
In an alternative embodiment of the present invention, the drive magnets may also be arranged horizontally.
In an advantageous embodiment of the present invention, the drive magnet arrangement contains pairs of opposing drive magnets with the stator arranged between them. This measure makes it possible to achieve a high propulsion force with a relatively low stator current. This reduces the losses on the cables.
The stator may have two helical windings arranged side by side in the longitudinal direction or one above the other. In this way, each of the poles of the magnet can contribute toward the drive of the vehicle, and a simple stator design is possible. As an alternative, it is also possible for the stator winding to form a figure eight in the longitudinal direction as seen from above.
In another embodiment of the present invention with a vertical arrangement of the drive magnets, the drive system is also designed as a guidance system. This permits simple control of the lateral guidance of the magnetically levitated vehicle which is completely decoupled from the drive function, although the same parts are used for the drive and for lateral guidance.
With a horizontal arrangement of the drive magnets, the drive system is may be also designed as a suspension system. This permits simple control of the suspension system of the magnetically levitated vehicle which is completely decoupled from the drive function, although the same parts are used for the drive and for suspension.
In an especially advantageous embodiment of the present invention, the suspension magnets of a suspension magnet arrangement mounted in the vehicle are arranged horizontally with their magnetic axes running between the two magnet poles and running across the longitudinal direction of the guideway, in particular beneath the guideway, so that the magnet poles arranged in succession in the longitudinal direction have the same polarity. This measure also prevents alternating fields from developing in the guideway, so a ferromagnetic mounting plate can be use
Blankenship G
Pape Joseph D.
Siemens Aktiengesellschaft
Young & Thompson
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